Permaculture is a relatively modern term for practices with an ancient history of aiding the development of sustainable living systems. To answer this question about Permaculture, let us consider the following sub-questions…

How does Permaculture use appropriately mixed trees, crop plants and wild vegetation to support each other, yielding maximal productivity with minimal inputs?

Dryland permaculture or agroforestry systems (Fig. 7) featuring mixed tree, shrub and herbaceous vegetation are ideally suited for exploiting and safeguarding all resources in scarce environments. The trees exploit the upper levels of light, and recover the deep lying soil reserves of moisture and nutrients. In this way, a far larger resource inventory is made available to the ecosystem, from deep soil to many meters above ground, strengthening ecosystem resilience and total system productivity. The tree canopies provide further benefits such as wind break, and reduce the intensity of often fierce rainstorms to protect soil and plants from mechanical damage.

Perennial shrubs intercropped with trees exploit the medium heights both above and below ground, are often highly tolerant to climate extremes and can provide food and fodder. Annual herbaceous vegetation is active in winter (in Israel) or during the rainy season in general, and exploits resources and moisture in the top soil.

The various vegetation types in such permacultures systems support each other as follows: the trees shade the lower vegetation layers thus reducing evaporation losses and radiation stress. They also provide leaf litter to protect and improve topsoil. The trees also recover nutrients from deep soil, and provide windbreak. Intermediate shrub vegetation is excellent in erosion control. Both trees and shrubs provide leave litter to protect and enrich topsoil by forming an organic litter layer for maximizing nutrient availability and water infiltration. The annual vegetation thriving to high productivity in partial shade and high quality top soil provides livestock fodder and the roots further enrich the topsoil with organic matter.

Fig. 7: This schematic representation of dryland agroforestry presents how a suitable mixture of perennials, trees and annual plants results in the best possible resource exploitation. Trees recover resources from deep soil, provide partial shade, and litter to enrich topsoil. These favorable conditions are exploited by shrubs and annuals for providing maximum amounts of biomass, food or fodder possible. Incorporating large numbers of useful fruit trees can transform such systems to provide several times the amounts of product compared to rain-fed monocultures.

The permanent organic litter layer provides a persistent nutrient reserve which is a de-facto slow-release fertilizing mechanism by decomposition in proportion to available moisture. As a result a maximally productive symbiosis is created where maximal water use efficiency is achieved under any given climatic conditions.

How does Permaculture support soil nutrition? Do the deep rooted nitrogen fixing trees provide compost and nutrients continuously?

This is exactly the process. Nutrient supply and soil cover are the major limitations for ecosystem productivity in all climate zones. In dryland areas nutrient supply to plants, and especially annual plants, is specifically critical as low soil moisture allows formation of shallow roots only so that deeper lying nutrient reserves are inaccessible to annual plants. Similarly, only a thin topsoil layer is being enriched with nutrients and SOM. As exposed dryland soils are prone to wind and water erosion, valuable nutrients, litter and seeds are drained from the ecosystem and irreversibly lost.

Permaculture systems overcome these deficiencies in several ways:

A) The combination of trees, other perennials and annual vegetation fix, store and recover nutrient pools from various soil depths and layers depositing them on the topsoil where they are made available to plants by biomass decomposers.

B) Incorporation of nitrogen fixing plants and trees into Permaculture systems will increase the amount of nitrogen to the ecosystem significantly as nitrogen is the most critical nutrient determining overall biological productivity.

The nitrogen cycle (Fig. 8) is composed of a number of biochemical processes turning over nitrogen between its gaseous form in the atmosphere, biochemically fixed nitrogen in living organisms and plant litter, and inorganic soil minerals such as nitrate or ammonia turning over in the soil. Nitrogen can be lost from the ecosystem by erosion, or by denitrification, the microbial transformation nitrogen minerals into nitrogen gas. Vice versa, some bacteria often living in symbiosis with plant roots are able to fix atmospheric nitrogen into biomass and nitrate, and pollution and lightning also contribute nitrate to the biosphere. The interplay between nitrogen influx, fixation, denitrification and erosion losses ultimately determine the bio-accessible nitrogen pool in the ecosystem and thus biological productivity, soil and standing biomass.

Fig. 8: The nitrogen cycle describes the biochemical pathways by which nitrogen cycles from atmospheric gas into the biosphere and soil minerals, and back to the gaseous form. The amount of nitrogen cycling inside an ecosystem (figures 9 and 10) to a large extent determines its biological productivity and its standing biomass.

An ecosystem rich in deep rooted perennial plants therefore automatically has access to far larger amounts of nutrients than an ecosystem based on scarce annual vegetation only. Our soil analyses have revealed that minor, but significant reserves of nitrogen minerals, phosphate and potassium are distributed evenly across the whole soil depth profile, meaning that deep-rooted perennials have access to an almost unlimited amount of nutrients, while annual vegetation has access to less than 10% of this nutrient pool.

Fig. 9: Holistic representation of the contributions of nitrogen fixing trees to enhancing the ecosystem nitrogen pool and fertility. Besides inputs from the atmosphere (green arrow), the trees recover nitrogen (and other nutrients) from deep soil, and have symbiotic nitrogen fixing bacteria (green-yellow arrows. The trees shed nutrient rich leave litter replenishes top soil with nutrients and reduced erosion and evaporation. Presence of the trees consequently maintains a much larger, and ever increasing nitrogen pool and productivity than comparable degraded dryland with much lower productivity (Fig. 10).

Fig. 10: In degraded soils free of perennial plants, nitrogen influx from the atmosphere is only partly exploited by vegetation resulting in a very small available nitrogen pool and low ecosystem productivity.

Even though dryland Permaculture systems require little water or fertilizer, can they still produce a lot of food and fodder?

Conserved dryland ecosystems can provide very significant amounts of biomass as food or fodder. Edible dryland forest systems can provide a wide range of fruit, oil and wood products, together with fodder from leaves and annual vegetation. Productivities of up to 10 tons of biomaterials in arid and semi-arid areas are not impossible to achieve, and this is about 10 times higher than today’s degraded dryland ecosystem productivities (Fig. 11).

Fig 11: Three years old organic Pomegranate and fig-plantations (above) at Project Wadi Attir, co-producing fruit and annual vegetation as fodder while protecting and restoring the soil and enhancing water use efficiency. Located in a water catchment terrace this system likely has annual biomass productivity above 10 tons per hectare and year with corresponding carbon sequestration into biomass and soil.

A wide range including extreme dryland trees provide valuable fruit, seeds including valuable seed oils, and this normally during the dry season when other sources of food are scarce. Project Wadi Attir has planted species such as Ziziphus, Prosopis, Carob, Balanites and similar that are well known by indigenous people as valuable survival aids during the long dry seasons. Mediterranean species such as olives, pomegranate, grapes, figs, almonds and dates have been domesticated to provide large amounts of valuable fruit and seeds even under arid or hyper-arid conditions allowing survival under the most hostile environmental conditions. In addition to direct tree products, many dryland trees flower during the dry season providing valuable nectar to honey-bees and other insects, maintaining healthy pollinator populations throughout the year while producing valuable honey and benefiting agricultural crops as required.

Fig. 12: Eucalyptus (top picture), Ziziphus, Acacia and other dryland trees flower during the dry season providing valuable nectar to honey bees. Project Wadi Attir has established honey bee hives (bottom) for enhancing pollination activities, and for production of valuable organic honey.

How can the high plant and animal diversity of Permaculture systems create pest resilient ecosystems?

Modern monocultures provide ideal breeding ground for a huge number of pests that accumulate exponentially with time and demand ever increasing amounts and treatment intensities with growing costs and environmental impact.

In mixed Permaculture systems those destructive feedback mechanisms are broken, because each species creates a wide range of associations and interactions with multiple organisms to finally create a carefully balanced ecosystem where no pests are able to proliferate to harmful levels, while beneficiary organisms such as pollinators, predators and nitrogen fixing plants are enriching and stabilizing the ecosystem and food pyramids.

Table 1: Some of the increasingly found beneficiary organisms and their key activities

Furthermore among the annual plants growing on site, a significant number are nitrogen fixing, and about 1/3 of the trees and shrubs planted are nitrogen fixing. Together those plants will contribute to enhance biological nitrogen reserves and overall plant productivity.

The key input of Permaculture approaches into sustainable agricultural production is restoration of a functional soil profile including a healthy O-horizon, which will give rise to the necessary microbial and micro-faunal balance to enhance plant productivity and suppress the spreading of pathogenic organisms. A major service provided by a rich and diverse soil microfauna is enhancing tree growth by associated fungi called mycorrhiza that have a wide range of beneficial functions and participate among others in mobilizing soil nutrients and moisture not accessible to the tree roots.

A diverse and mixed Permaculture style agricultural system

Another classical example are nematodes, that are being represented as the major scourge of modern agriculture. Soil steaming (e. g. by methyl-bromide) is an efficient method to kill nematodes before planting a crop, but indiscriminately eliminates both harmful and beneficial soil fauna. Depending on the species, a nematode may be beneficial or detrimental to plant health. From agricultural and horticulture perspectives, the predatory ones will kill garden pests like cutworms and corn earworm moths, and the pest nematodes attacking plants, or acting as vectors spreading plant viruses. Rotations of plants with nematode-resistant species or varieties are one means of managing parasitic nematode infestations. For example, marigolds, grown over one or more seasons (the effect is cumulative), can be used to control nematodes. 90 percent of nematodes reside in the top 15 cm of soil. Nematodes do not decompose organic matter, but, instead, are parasitic and free-living organisms that feed on living material. Nematodes can effectively regulate bacterial population and community composition – they may eat up to 5,000 bacteria per minute. Also, Nematodes can play an important role in the nitrogen cycle by way of nitrogen mineralization. Consequently rich organic soil with high microfaunal diversity and mixed crops will be protected from nematode or other pest attacks due to the mutual regulatory activities of the huge diversity of soil fauna and soil microorganisms.

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Why do Permaculture systems require very low inputs of pesticides, fertilizer and water?

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